Mask blanks, phase shift mask, and method for manufacturing semiconductor device

ABSTRACT

The phase shift film has a function to transmit the exposure light of the ArF excimer laser at a transmittance of not less than 10% and not more than 20%, and a function to generate a phase difference of not less than 150 degrees and not more than 190 degrees between the exposure light transmitted through the phase shift film and the exposure light transmitted through the air for the same distance as a thickness of the phase shift film. The phase shift film is made of a material containing a metal, silicon, nitrogen, and oxygen. A ratio of the metal content to the total content of the metal and silicon in the phase shift film is not less than 5% and not more than 10%, the oxygen content in the phase shift film is 10 atom % or more, and the silicon content in the phase shift film is three times or more the oxygen content.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2016/051378 filed Jan. 19, 2016, claiming priority based onJapanese Patent Application No. 2015-060699 filed Mar. 24, 2015, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a mask blank, a phase shift maskmanufactured using the mask blank, and a method for manufacturing thephase shift mask. The present invention also relates to a method formanufacturing a semiconductor device using the phase shift mask.

BACKGROUND ART

In a manufacturing process of a semiconductor device, a fine pattern isgenerally formed using a photolithographic method. In the formation ofthe fine pattern, multiple transfer masks are usually used. Refinementof a pattern for the semiconductor device requires shortening of awavelength of an exposure light source used in photolithography, inaddition to the refinement of a mask pattern formed in the transfermask. Nowadays, the exposure light sources used in the manufacture ofsemiconductor devices are shifting from KrF excimer lasers (wavelength:248 nm) to ArF excimer lasers (wavelength: 193 nm), that is, shorterwavelength light sources are increasingly used.

The types of transfer masks include a conventional binary mask includinga light shielding film pattern made of a chromium-based material on atransparent substrate, and a half tone phase shift mask. A molybdenumsilicide (MoSi)-based material is widely used for a phase shift film ofthe half tone phase shift mask. However, as disclosed in Patent Document1, it has been discovered recently that the MoSi-based film has a lowresistance to exposure light of an ArF excimer laser (that is, so-calledArF light fastness is low). In Patent Document 1, the ArF light fastnessis enhanced by subjecting the MoSi-based film after formation of apattern to the plasma treatment, ultraviolet (UV) light irradiationtreatment, or heat treatment to form a passivation film on a surface ofthe pattern of the MoSi-based film.

Patent Document 2 discloses a defect repairing technique in which axenon difluoride (XeF₂) gas is supplied to a black defect portion of alight shielding film while irradiating the portion with electron beamsto etch and remove the black defect portion (the defect repair byirradiation of charged particles such as electron beams as above ishereafter simply referred to as EB defect repair). While the EB defectrepair was originally used to correct black defects in an absorber filmof a reflective mask for extreme ultraviolet lithography (EUVlithography), it has recently been used for correcting black defects ofa MoSi half tone mask as well.

Patent Document 3 discloses the mask structure of a half tone phaseshift mask with a high transmittance. Since the conventional phase shiftfilm with a high transmittance formed of a two-layer structure easilythickens, it has the problem that the pattern easily collapses when afine optical proximity correction (OPC) pattern is formed. The phaseshift film of Patent Document 3 is thinner than the phase shift film ofa two-layer structure, and thus, the pattern does not easily collapseeven if the fine OPC pattern is formed.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application Publication 2010-217514

Patent Document 2: PCT Application Japanese Translation Publication2004-537758

Patent Document 3: Japanese Patent Application Publication 2010-9038

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In a half tone phase shift mask used in photolithography by applying ArFexcimer laser light as exposure light (hereinafter also referred to asArF exposure light), it is necessary for a half tone phase shift film(hereinafter simply referred to as “phase shift film”) to simultaneouslyhave a function to transmit the ArF exposure light at a predeterminedtransmittance, and a function to generate a predetermined phasedifference (phase shift amount) between the ArF exposure lighttransmitted through the phase shift film and the light transmittedthrough the air for the same distance as a thickness of the phase shiftfilm. A phase shift film with a property of a transmittance of less than10% to the ArF exposure light has been widely used, and the generalphase shift amount has been around 180 degrees. A material for a phaseshift film of a single layer structure (A single layer structureincluding a region where oxidation of its surface layer is inevitable.The single layer structure is hereinafter deemed as including anoxidized region on its surface layer, excluding when particularlyreferring to the oxidized region of the surface layer) whichsimultaneously satisfies both conditions of the phase shift amount andthe transmittance to the ArF exposure light as mentioned above and iscapable of achieving a lesser film thickness is relatively limited. Amaterial formed from molybdenum silicide nitride (MoSiN) satisfies theseconditions, and has been used widely.

Nowadays, there is an increased need for a phase shift film with a hightransmittance (phase shift film having a transmittance of 10% or more)in order to obtain a higher phase shift effect for the transmitted lightpassing nearby a pattern edge in a half tone phase shift mask. For aconventional phase shift film of a single layer structure made of MoSiN,in order to ensure a predetermined phase difference while achieving thetransmittance of 10% or more, the molybdenum content in the phase shiftfilm needs to be decreased, for example, a ratio [%] of the molybdenumcontent [atom %] divided by the total content [atom %] of molybdenum(Mo) and silicon (Si) in the phase shift film (hereinafter referred toas “Mo/[Mo+Si] ratio”) needs to be 4% or less. However, the decrease inmolybdenum content in the phase shift film gives rise to a problem ofthe decrease in film conductivity. The decrease in molybdenum content inthe phase shift film also gives rise to a problem of the low etchingrate in the above-described EB defect repair for a black defect in thephase shift film.

The material used for the phase shift film includes molybdenum silicideoxynitride (MoSiON). While the phase shift film of a single layerstructure made of MoSiON is thicker than the phase shift film of asingle layer structure made of MoSiN, it can have a transmittance of 10%or more while ensuring the predetermined phase difference even if themolybdenum content is relatively high (e.g., Mo/[Mo+Si] ratio of 5% ormore). However, it was demonstrated that the mask blank including thephase shift film of a single layer structure made of MoSiON has thefollowing problem.

When a black defect is found in a phase shift film during a maskinspection in the manufacture of a phase shift mask from a mask blank,it is often repaired by the EB defect repair. It was newly found thatwhen the black defect in the phase shift film of a single layerstructure made of MoSiON is repaired by the EB defect repair, thedetection of an etching end point for detecting a boundary between thephase shift film and the transparent substrate becomes more difficultthan in the phase shift film of a single layer structure made of MoSiN.

The present invention was made to solve the above existing problems. Itis an object of the present invention to provide a mask blank whichincludes a phase shift film with a high transmittance on a transparentsubstrate, wherein even if the phase shift film has optical propertiesthat it has a transmittance of 10% or more while ensuring apredetermined phase difference, it is relatively easy to detect theetching end point for detecting a boundary between the phase shift filmand the transparent substrate during the EB defect repair, so that thehighly accurate EB defect repair is possible. It is another object ofthe present invention to provide a high-transmittance phase shift maskwith fewer black defects, which is manufactured using the mask blank.Further, it is still another object of the present invention to providea method for manufacturing the phase shift mask. It is yet anotherobject of the present invention to provide a method for manufacturing asemiconductor device using the phase shift mask.

Means for Solving Problems

In order to solve the above problems, the present invention includes thefollowing configurations.

Configuration 1

A mask blank including a phase shift film on a transparent substrate,

wherein the phase shift film has a function to transmit exposure lightof an ArF excimer laser at a transmittance of not less than 10% and notmore than 20%, and a function to generate a phase difference of not lessthan 150 degrees and not more than 190 degrees between the exposurelight transmitted through the phase shift film and the exposure lighttransmitted through the air for the same distance as a thickness of thephase shift film;

wherein the phase shift film is made of a material containing a metal,silicon, nitrogen, and oxygen;

wherein a ratio of the metal content to the total content of the metaland silicon in the phase shift film is not less than 5% and not morethan 10%;

wherein the oxygen content in the phase shift film is 10 atom % or more;and

wherein the silicon content in the phase shift film is three times ormore the oxygen content.

Configuration 2

The mask blank according to Configuration 1, wherein the oxygen contentin the phase shift film is 20 atom % or less.

Configuration 3

The mask blank according to Configuration 1 or 2, wherein the nitrogencontent in the phase shift film is 30 atom % or more.

Configuration 4

The mask blank according to any one of Configurations 1 to 3, whereinthe nitrogen content in the phase shift film is 45 atom % or less.

Configuration 5

The mask blank according to any one of Configurations 1 to 4, whereinthe phase shift film is formed in contact with a surface of thetransparent substrate.

Configuration 6

The mask blank according to any one of Configurations 1 to 5, whereinthe phase shift film has a thickness of 90 nm or less.

Configuration 7

The mask blank according to any one of Configurations 1 to 6, whereinthe phase shift film has in its surface layer a layer having the oxygencontent higher than the portion of the phase shift film excluding thesurface layer.

Configuration 8

The mask blank according to any one of Configurations 1 to 7, includinga light shielding film on the phase shift film.

Configuration 9

A phase shift mask, wherein a transfer pattern is formed in the phaseshift film of the mask blank according to Configuration 8, and a lightshielding band pattern is formed in the light shielding film.

Configuration 10

A method for manufacturing a phase shift mask using the mask blankaccording to Configuration 8, including the steps of:

forming a transfer pattern in the light shielding film by dry etching,

forming the transfer pattern in the phase shift film by dry etching withthe light shielding film having the transfer pattern as a mask, and

forming the light shielding band pattern in the light shielding film bydry etching with a resist film having a light shielding band pattern asa mask.

Configuration 11

A method for manufacturing a semiconductor device, including the stepof:

using the phase shift mask according to Configuration 9 to transfer thetransfer pattern to a resist film on a semiconductor substrate byexposure.

Configuration 12

A method for manufacturing a semiconductor device, including the stepof:

using the phase shift mask manufactured by the method for manufacturinga phase shift mask according to Configuration 10 to transfer thetransfer pattern to a resist film on a semiconductor substrate byexposure.

Effect of the Invention

The mask blank of the present invention includes a phase shift film on atransparent substrate, and it is featured in that the phase shift filmis made of a material containing a metal, silicon, nitrogen, and oxygen;a ratio of the metal content to the total content of metal and siliconin the phase shift film is not less than 5% and not more than 10%; theoxygen content in the phase shift film is 10 atom % or more; and thesilicon content in the phase shift film is three times or more theoxygen content. By configuring the mask blank to have such a structure,the phase shift film can simultaneously ensure a function to transmitthe exposure light from the ArF excimer laser at a transmittance of 10%or more, and a function to generate a phase difference of not less than150 degrees and not more than 190 degrees between the exposure lighttransmitted through the phase shift film and the exposure lighttransmitted through the air for the same distance as the thickness ofthe phase shift film. In addition, the phase shift film facilitates thedetection of an etching end point for detecting a boundary between thephase shift film and the transparent substrate when the EB defect repairis carried out, such that the insufficient defect repair and inadvertentdigging of the transparent substrate can be avoided, thereby improvingthe accuracy of the EB defect repair.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a structure of a mask blankaccording to an embodiment of the present invention.

FIGS. 2(a) to 2(g) are schematic cross-sectional views showing amanufacturing process of a phase shift mask according to the embodimentof the present invention.

DESCRIPTION OF THE EMBODIMENT

The embodiment of the present invention is described below.

[Mask Blank and Manufacture Thereof]

The inventors made a diligent study on a high-transmittance phase shiftfilm of a single layer structure made of metal silicide oxynitride, suchas MoSiON as the representative, and its composition, which enable apractically sufficient processing speed and easy detection of an etchingend point for detecting a boundary between the phase shift film and thetransparent substrate during the EB defect repair, thereby achieving theEB defect repair with high accuracy. The phase shift film as a subjectmatter of the embodiment of the present invention is a film that canensure a predetermined phase difference (not less than 150 degrees andnot more than 190 degrees) and a high transmittance (not less than 10%and not more than 20%) with respect to the exposure light (ArF excimerlaser light). The optical properties of the phase shift film provide ahigh edge enhancement effect, and thus improve, in the transfer usingthe phase shift mask, resolution and focus tolerance. Also, the phaseshift film configured to have a single layer structure improves a sidewall shape upon forming a phase shift pattern by the dry etching ascompared to the phase shift film of a laminated structure comprised oftwo or more layers. Further, since the phase shift film configured tohave a single layer structure can reduce man-hours in the manufacturingprocess and the number of steps in the film formation as compared to thephase shift film of a laminated structure comprised of two or morelayers, the defect generation can be restrained. Therefore, it ispossible to reduce the number of sections which are to be subjected tothe defect repair.

First, optically-required values of the phase shift film required in thepresent invention are described together with the reasons. Then, thematerial composition of the phase shift film is described, which cansatisfy the optically-required values and enable the highly accurate EBdefect repair (during which the end point can be detected with highaccuracy).

The phase shift film should have a transmittance of 10% or more withrespect to the ArF exposure light from the ArF excimer laser lightsource at a wavelength of 193 nm. This can provide light intensitydistribution in which the vicinity of the pattern edge is furtheremphasized in comparison to the conventional half tone phase shift mask,which improves the transfer performance such as resolution and focustolerance of the phase shift mask manufactured using this phase shiftfilm.

However, if the transmittance of the phase shift film becomes too high,unintended light intensity distribution referred to as a sub-peak easilyoccurs, which is caused by an interference between the diffracted lightfrom the transfer pattern and the light transmitted through a fieldportion comprised of portions of the phase shift film other than thephase shift pattern. The light intensity in the portion of the sub-peakis enhanced, which develops a defect to be transferred (this is referredto as “sub-peak transfer”). In view of suppression of the unintendedsub-peak transfer, the phase shift film preferably has a transmittanceof 20% or less with respect to the ArF exposure light. In order toincrease the tolerance for various pattern layouts to ease restrictionson the pattern layouts, the phase shift film preferably has thetransmittance of 15% or less with respect to the ArF exposure light.

Moreover, the phase shift film should be adjusted such that the phasedifference between the ArF exposure light transmitted therethrough andthe light transmitted through the air for the same distance as thethickness of the phase shift film is not less than 150 degrees and notmore than 190 degrees in order to obtain a suitable phase shift effect.The upper limit of the phase difference in the phase shift film is morepreferably 180 degrees or less. This is because it is possible to reducethe effect of increase in phase difference caused by the slight etchingof the transparent substrate during the dry etching for forming apattern in the phase shift film. This is also because the recent methodsof irradiating the phase shift mask with the ArF exposure light from theexposure apparatus often apply incidence of the ArF exposure light froma direction tilted at a predetermined angle to the direction vertical toa film surface of the phase shift film.

In the EB defect repair of the phase shift film made of metal silicideoxynitride, three elements are practically important for highly accurateEB defect repair: the etching rate of metal silicide oxynitride, adifference in etching rate between metal silicide oxynitride and thesubstrate, and accuracy of detection of an etching end point. Thesecharacteristics need to be satisfied without compromising therequirements for providing the above described transmittance and phasedifference required for the phase shift film.

A metallic element in the metal silicide oxynitride is preferably atransition metal element. While molybdenum (Mo) has been widely used asthe transition metal element contained in the phase shift film, thetransition metal element is not limited thereto. The transition metalelement to be contained in the phase shift film includes any one or moremetallic elements of tantalum (Ta), tungsten (W), titanium (Ti),chromium (Cr), hafnium (Hf), nickel (Ni), vanadium (V), zirconium (Zr),ruthenium (Ru), rhodium (Rh), zinc (Zn), niobium (Nb), and palladium(Pd). Further, the metallic elements other than transition metalelements include aluminum (Al), indium (In), tin (Sn), gallium (Ga), andthe like.

In the EB defect repair, when a black defect is irradiated with electronbeams, at least any one of Auger electrons, secondary electrons,characteristic X-rays, and backscattered electrons emitted from theirradiated portion is detected, thereby detecting an etching end point.For example, in the case of detecting Auger electrons emitted from theportion irradiated with electron beams, the change of materialcomposition is mainly observed by Auger electron spectroscopy (AES). Inthe case of detecting secondary electrons, the change of surface shapein a SEM image is mainly observed. In the case of detectingcharacteristic X-rays, the change of material composition is mainlyobserved by energy dispersive X-ray spectrometry (EDX) orwavelength-dispersive X-ray spectrometry (WDX). In the case of detectingbackscattered electrons, the change of material composition and crystalstate is mainly observed by electron beam backscatter diffraction(EBSD).

In the EB defect repair of the phase shift film made of the metalsilicide oxynitride, a fluorine-based gas in an unexcited state (XeF₂,XeF₄, XeF₆, XeOF₂, XeOF₄, XeO₂F₂, XeO₃F₂, XeO₂F₄, ClF₃, ClF, BrF₅, BrF,IF₃, IF₅, and the like are applicable, and XeF₂ is particularlypreferable) is supplied to a black defect portion in the phase shiftfilm while irradiating the portion with electron beams, thereby etchingand removing the black defect portion. The etching rate at this pointdepends on the ratio [%] of the content [atom %] of metal (M) divided bythe total content [atom %] of metal and silicon (Si) (hereinafterreferred to as “M/[M+Si] ratio”). As a result of close examination ofthe etching rate in relation to this ratio, it was found that thepractically sufficient etching rate is ensured when the M/[M+Si] ratioof the phase shift film made of the metal silicide oxynitride is 5% ormore. It was additionally found that the etching selectivity in relationto the transparent substrate mainly including silicon oxide can also besufficiently ensured.

Within the range of the M/[M+Si] ratio up to about 34%, absorption ofthe exposure light (ArF exposure light) tends to increase as theM/[M+Si] ratio in the phase shift film increases. When the M/[M+Si]ratio becomes too high, the oxygen or nitrogen content should besignificantly increased in order to realize the phase shift filmtransmittance of from 10% to 20% with respect to the exposure light.However, a refractive index tends to lower as the oxygen content in thephase shift film increases, and thus, it becomes difficult to avoid thesignificant increase in film thickness for ensuring the predeterminedphase difference. When the phase shift film thickens, it gives rise tothe problem that a fine mask pattern on a mask collapses, or the bias(EMF bias) due to an electromagnetic field effect becomes large in amask pattern. It was found that the upper limit of the M/[M+Si] ratioshould be preferably 10% in order to control the pattern collapse orkeep the EMF bias within an acceptable range. It was also found thatwhen the M/[M+Si] ratio is 10% or less, the resistance of the phaseshift film to an accumulated exposure amount of the ArF exposure lightis practically sufficient.

In order to keep the M/[M+Si] ratio of 5% or more in the phase shiftfilm while providing the optical property that the transmittance to theexposure light is 10% or more, the oxygen content should be equal to orgreater than a predetermined amount. As a result of evaluation of theamount, it was found that the oxygen content in the phase shift filmshould be 10 atom % or more. Additionally, in order to further enhancethe transmittance of the phase shift film with respect to the exposurelight, the oxygen content is preferably 12 atom % or more. However, inorder to easily detect an etching end point in the EB defect repair, theoxygen content in the phase shift film should be 20 atom % or less,preferably 18 atom % or less, further preferably 15 atom % or less.

As described above, the phase shift film made of metal silicideoxynitride contains certain amounts or more of silicon and oxygen. Thetransparent substrate made of, for example, synthetic quartz mainlycontains silicon and oxygen, and constituent elements of the phase shiftfilm and the transparent substrate are relatively similar to each other.Therefore, there is a problem that the detection of the etching endpoint is difficult no matter which detection method as described aboveis used in the EB defect repair. However, by configuring the siliconcontent percentage in the phase shift film to be three times or more theoxygen content percentage in this embodiment, the obvious difference indetection signal before and after the etching end point is caused, whichenables the detection of the etching end point.

In order to make the phase shift film as thin as possible whilecontrolling the transmittance and phase difference with respect to theexposure light to be respective desired values, it is effective tocontain nitrogen (N) so that the extinction coefficient k and refractiveindex n of the phase shift film with respect to the exposure light aregreater than the case when only the oxygen (O) is contained. Bycontaining nitrogen within the range of not less than 30 atom % and notmore than 45 atom % in the phase shift film, the phase shift film canhave the thickness of 90 nm or less as described below and the abovementioned desired transmittance and phase difference, which is effectivein forming a fine pattern on a photomask and reducing the bias (EMFbias) due to the electromagnetic field effect.

The material of the phase shift film may contain, in addition to themetal, silicon, nitrogen, and oxygen, 10 atom % or less of elementsother than these main constituent elements. As long as the total contentof the elements other than the main constituent elements in the phaseshift film is 10 atom % or less, an effect on various optical propertiesand various properties related to the EB defect repair for the phaseshift film is small, which is acceptable.

The overall structure of the mask blank is described below withreference to FIG. 1.

FIG. 1 is a cross-sectional view showing a structure of a mask blank 100according to an embodiment of the present invention. The mask blank 100of the present invention shown in FIG. 1 has a structure in which aphase shift film 2, a light shielding film 3, and a hard mask film 4 arelaminated in this order on a transparent substrate 1.

The transparent substrate 1 can be formed from quartz glass,aluminosilicate glass, soda-lime glass, low thermal expansion glass(SiO₂—TiO₂ glass, etc.), and the like, in addition to synthetic quartzglass. Among the above, synthetic quartz glass is particularlypreferable as a material for forming the transparent substrate of themask blank since it has a high transmittance to the ArF exposure lightand also has sufficient stiffness not to be easily deformed.

The phase shift film 2 is preferably formed in contact with a surface ofthe transparent substrate 1. This is because a film made of a materialcausing difficulty in EB defect repair (e.g., a film made of achromium-based material) preferably does not exist between thetransparent substrate 1 and the phase shift film 2 during the EB defectrepair.

The material of the phase shift film 2 is metal silicide oxynitridehaving the above described composition ratio.

The thickness of the phase shift film 2 is preferably at least 90 nm orless because film thinning can reduce the EMF bias. Thus, the thicknessof the phase shift film 2 is further preferably 85 nm or less, and morepreferably 80 nm or less. Further, the thinning of the phase shift filmcan suppress a failure due to the pattern collapse on the mask, andimprove the yield of the phase shift mask.

In order to satisfy various conditions for the above optical propertiesand thickness of the phase shift film 2, the refractive index n of thephase shift film with respect to the exposure light (ArF exposure light)is preferably 1.9 or more, and more preferably 2.0 or more. Further, therefractive index n of the phase shift film is preferably 3.1 or less,and more preferably 2.7 or less. The extinction coefficient k of thephase shift film 2 with respect to the ArF exposure light is preferably0.26 or more, and more preferably 0.29 or more. Further, the extinctioncoefficient k of the phase shift film 2 is preferably 0.62 or less, andmore preferably 0.54 or less.

The refractive index n and extinction coefficient k of a thin filmincluding the phase shift film 2 are not determined only by thecomposition of the thin film. Factors such as film density and crystalcondition of the thin film also affect the refractive index n andextinction coefficient k. Therefore, the conditions in forming the thinfilm by the reactive sputtering are adjusted, so that the thin film isformed to have a desired refractive index n and extinction coefficientk. The effective conditions for configuring the phase shift film 2 tohave the refractive index n and extinction coefficient k within theabove-described ranges include, but are not limited to, the adjustmentof a ratio of a noble gas and a reactive gas (such as oxygen gas ornitrogen gas) in a mixed gas in forming the phase shift film 2 by thereactive sputtering. Rather, there are a wide variety of conditions suchas a pressure in a film forming chamber, power applied to the sputtertarget, and a positional relationship between the target and thetransparent substrate 1 such as a distance in forming the phase shiftfilm 2 by the reactive sputtering. These film forming conditions arespecific to a film forming apparatus, and are adjusted arbitrarily sothat the phase shift film 2 to be formed has the desired refractiveindex n and extinction coefficient k.

While the phase shift film 2 is formed by the sputtering, anysputtering, such as DC sputtering, RF sputtering, and ion beamsputtering, may be applied. In the case where the target used has lowconductivity, application of RF sputtering or ion beam sputtering ispreferable. However, in view of film forming rate, application of RFsputtering is more preferable.

The phase shift film 2 preferably has in its surface layer a layerhaving the oxygen content higher than the portion of the phase shiftfilm 2 excluding the surface layer (which is hereafter simply referredto as a surface oxidized layer). The phase shift film 2 which includesin its surface layer the layer having the high oxygen content has a highresistance to cleaning liquid used in a cleaning step in the maskmanufacturing process or the mask cleaning for repeatedly using thephase shift mask. Various oxidization treatments are applicable as amethod of forming the surface oxidized layer of the phase shift film 2.The oxidization treatments include, for example, a heat treatment in agas containing oxygen such as the atmosphere, a light irradiationtreatment using a flash lamp, etc. in a gas containing oxygen, atreatment to bring ozone and oxygen plasma into contact with theuppermost layer, etc. It is particularly preferable to form the surfaceoxidized layer in the phase shift film 2 through the heat treatment orlight irradiation treatment using a flash lamp, etc. where an effect toreduce film stress of the phase shift film 2 can be obtainedsimultaneously. The thickness of the surface oxidized layer of the phaseshift film 2 is preferably 1 nm or more, and more preferably 1.5 nm ormore. Further, the thickness of the surface oxidized layer of the phaseshift film 2 is preferably 5 nm or less, and more preferably 3 nm orless.

The mask blank 100 has a light shielding film 3 on the phase shift film2. Generally, in a binary transfer mask, an outer peripheral regionoutside the region where a transfer pattern is formed (transfer patternforming region) is required to ensure optical density (OD) of not lessthan a predetermined value such that, upon the exposure transfer to aresist film on a semiconductor wafer using an exposure apparatus, theresist film will not be affected by the exposure light transmittedthrough the outer peripheral region. In this regard, the same holds fora phase shift mask. Usually, the outer peripheral region of a transfermask including a phase shift mask desirably has OD of 3.0 or more, andat least 2.8 or more is necessary. The phase shift film 2 has a functionto transmit the exposure light at a predetermined transmittance, and itis difficult to ensure the optical density of a predetermined valuerequired in the outer peripheral region with the phase shift film 2alone. Therefore, the light shielding film 3 for ensuring the lackingoptical density should be laminated on the phase shift film 2 at thestage of manufacturing the mask blank 100. With such a structure of themask blank 100, a phase shift mask 200 (see FIG. 2) ensuring opticaldensity of the predetermined value in the outer peripheral region can bemanufactured by removing the light shielding film 3 in the region wherethe phase shift effect is used (basically, the transfer pattern formingregion) during manufacture of the phase shift mask 200.

When the intensity of light incident on a target film is I₀, and theintensity of light transmitted through the target film is I, the opticaldensity OD is defined by:OD=−log₁₀(I/I ₀).

Any of a single layer structure and a laminated structure comprised oftwo or more layers is applicable to the light shielding film 3. Further,the light shielding film of the single layer structure as well as eachlayer in the light shielding film of a laminated structure comprised oftwo or more layers can be configured to have approximately the samecomposition in a thickness direction of the film or the layer, or tohave a composition gradient in the thickness direction of the layer.

The mask blank 100 shown in FIG. 1 has a configuration in which thelight shielding film 3 is laminated on the phase shift film 2 withoutany film therebetween. For the light shielding film 3 in the case ofthis configuration, it is necessary to use the material which hassufficient etching selectivity to the etching gas used in forming apattern in the phase shift film 2.

The light shielding film 3 in this case is preferably made of a materialcontaining chromium. The materials containing chromium for forming thelight shielding film 3 can include a material containing chromium (Cr)and one or more elements selected from oxygen (O), nitrogen (N), carbon(C), boron (B), and fluorine (F), in addition to chromium metal. While achromium-based material is generally etched with a mixed gas of achlorine-based gas and an oxygen gas, the etching rate of the chromiummetal with respect to the etching gas is not so high. Considering theenhancement of etching rate in relation to the etching gas that is themixed gas of the chlorine-based gas and oxygen gas, the material forforming the light shielding film 3 preferably contains chromium and oneor more elements selected from oxygen, nitrogen, carbon, boron, andfluorine. Further, the material containing chromium for forming thelight shielding film can contain one or more elements of molybdenum(Mo), indium (In), and tin (Sn). Containing one or more elements ofmolybdenum, indium, and tin can increase the etching rate in relation tothe mixed gas of the chlorine-based gas and oxygen gas.

The mask blank of the present invention is not limited to the one shownin FIG. 1. It can also be configured such that another film (etchingstopper film) is provided between the phase shift film 2 and the lightshielding film 3. In this case, a preferable structure is that theetching stopper film is made of the material containing chromiumdescribed above, and the light shielding film 3 is made of a materialcontaining silicon.

The material containing silicon for forming the light shielding film 3can contain a transition metal, and can also contain metallic elementsother than the transition metal. The reason is that the pattern formedin the light shielding film 3 is basically a light shielding bandpattern in the outer peripheral region, which has an accumulatedradiation value of the ArF exposure light lower than in the transferpattern region, and that a fine pattern is rarely provided in this outerperipheral region, such that substantial problems hardly occur even ifthe ArF light fastness is low. Another reason is that containing atransition metal in the light shielding film 3 significantly enhancesthe light shielding performance compared to the light shielding film 3not containing a transition metal, so that the thickness of the lightshielding film 3 can be reduced. The transition metals to be containedin the light shielding film 3 include any one metal such as molybdenum(Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), hafnium(Hf), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium(Rh), niobium (Nb), and palladium (Pd), or an alloy thereof.

In this embodiment, the hard mask film 4 laminated on the lightshielding film 3 is made of a material which has the etching selectivitywith respect to the etching gas used for etching the light shieldingfilm 3. Accordingly, the thickness of the resist film can besignificantly reduced compared to the resist film directly used as amask for the light shielding film 3.

Since the light shielding film 3 needs to ensure the predeterminedoptical density to have a sufficient light shielding function, there isa limit on the reduction of its thickness. The thickness of the hardmask film 4 is sufficient as long as the hard mask film 4 can functionas an etching mask until the completion of dry etching for forming apattern in the light shielding film 3 immediately thereunder, andbasically the hard mask film 4 is not optically limited. Therefore, thethickness of the hard mask film 4 can be reduced significantly comparedto the thickness of the light shielding film 3. Since the thickness ofthe resist film made of an organic material is sufficient as long as theresist film can function as an etching mask until the completion of dryetching for forming a pattern in the hard mask film 4, the thickness ofthe resist film can be reduced significantly compared to the resist filmdirectly used as a mask for the light shielding film 3. Since the resistfilm can be thinned in this manner, the resist resolution can beimproved while preventing the collapse of the formed pattern. In thisway, while the hard mask film 4 laminated on the light shielding film 3is preferably made of the above described material, the presentinvention is not limited to this embodiment. Also, a resist pattern canbe formed directly on the light shielding film 3 in the mask blank 100without forming the hard mask film 4, and then used as a mask todirectly etch the light shielding film 3.

If the light shielding film 3 is made of the material containingchromium, the hard mask film 4 is preferably made of the materialcontaining silicon given above. Since the hard mask film 4 in this casetends to have low adhesiveness to the resist film made of an organicmaterial, it is preferable to treat the surface of the hard mask film 4with hexamethyldisilazane (HMDS) to enhance the surface adhesiveness.The hard mask film 4 in this case is more preferably made of SiO₂, SiN,SiON, etc.

Further, if the light shielding film 3 is made of the materialcontaining chromium, a material containing tantalum is also applicableas the material for the hard mask film 4, in addition to the above. Thematerial containing tantalum in this case includes, in addition totantalum metal, a material containing tantalum and one or more elementsselected from nitrogen, oxygen, boron, and carbon, for example, Ta, TaN,TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, and TaBOCN.

Further, if the light shielding film 3 is made of the materialcontaining silicon, the hard mask film 4 is preferably made of thematerial containing chromium given above.

In the mask blank 100, a resist film made of an organic material andhaving a thickness of 100 nm or less is preferably formed in contactwith the surface of the hard mask film 4. In the case of a fine patternto meet DRAM hp32 nm generation, a sub-resolution assist feature (SRAF)with 40 nm line width may be provided on a transfer pattern (phase shiftpattern) to be formed in the hard mask film 4. Even in such a case, across-sectional aspect ratio of the resist pattern is as low as 1:2.5,and thus, the collapse and falling off of the resist pattern can beprevented in rinsing and developing the resist film. The thickness ofthe resist film is more preferably 80 nm or less because the collapseand falling off of the resist pattern can be further prevented.

[Phase Shift Mask and Manufacture Thereof]

The phase shift mask 200 of this embodiment is featured in that atransfer pattern (phase shift pattern) is formed in the phase shift film2 of the mask blank 100, and a light shielding band pattern is formed inthe light shielding film 3. In the case of the configuration in whichthe mask blank 100 includes the hard mask film 4, the hard mask film 4is removed during manufacture of the phase shift mask 200.

The method for manufacturing a phase shift mask according to the presentinvention uses the mask blank 100 described above is featured byincluding the steps of: performing the dry etching, thereby forming atransfer pattern in the light shielding film 3; performing the dryetching using as a mask the light shielding film 3 having the transferpattern, thereby forming the transfer pattern in the phase shift film 2;and performing the dry etching using as a mask a resist film (secondresist pattern 6 b) having a light shielding band pattern, therebyforming the light shielding band pattern in the light shielding film 3.The method for manufacturing the phase shift mask 200 of the presentinvention is described below in accordance with the manufacturingprocess shown in FIGS. 2(a) to 2(g). The method explained here is themethod for manufacturing the phase shift mask 200 using the mask blank100 having the hard mask film 4 laminated on the light shielding film 3,wherein a material containing chromium is used for the light shieldingfilm 3, and a material containing silicon is used for the hard mask film4.

First, a resist film is formed in contact with the hard mask film 4 ofthe mask blank 100 by a spin coating method. Next, a first pattern,which is a transfer pattern (phase shift pattern) to be formed in thephase shift film, is drawn on the resist film with electron beams byexposure, and a predetermined treatment such as development isconducted, thereby forming a first resist pattern 5 a having the phaseshift pattern (see FIG. 2(a)). Subsequently, the dry etching with afluorine-based gas using the first resist pattern 5 a as a mask isperformed, so that the first pattern (hard mask pattern 4 a) is formedin the hard mask film 4 (see FIG. 2(b)).

Next, after removing the first resist pattern 5 a, the dry etching witha mixed gas of a chlorine-based gas and an oxygen gas using the hardmask pattern 4 a as a mask is performed, so that the first pattern(light shielding pattern 3 a) is formed in the light shielding film 3(see FIG. 2(c)). Subsequently, the dry etching with the fluorine-basedgas using the light shielding pattern 3 a as a mask is performed, sothat the first pattern (phase shift pattern 2 a) is formed in the phaseshift film 2, and at the same time the hard mask pattern 4 a is removed(see FIG. 2(d)).

Next, a resist film is formed on the mask blank 100 by the spin coatingmethod. Then, a second pattern, which is a pattern (light shieldingpattern) to be formed in the light shielding film 3, is drawn on theresist film with electron beams by exposure, and a predeterminedtreatment such as development is conducted, thereby forming a secondresist pattern 6 b having the light shielding pattern (see FIG. 2(e)).Since the second pattern is relatively large, the exposure drawing usingthe laser beam from a laser writer with high throughput may be appliedinstead of the exposure drawing using the electron beams.

Subsequently, the dry etching with the mixed gas of the chlorine-basedgas and oxygen gas using the second resist pattern 6 b as a mask isperformed, so that the second pattern (light shielding pattern 3 b) isformed in the light shielding film 3 (see FIG. 2(f)). Further, thesecond resist pattern 6 b is removed, and a predetermined treatment suchas cleaning is conducted, so that the phase shift mask 200 is obtained(see FIG. 2(g)).

There is no particular limitation on the chlorine-based gas used in thedry etching described above, as long as chlorine (Cl) is contained. Sucha chlorine-based gas includes, for example, Cl₂, SiCl₂, CHCl₃, CH₂Cl₂,and BCl₃. Also, there is no particular limitation on the fluorine-basedgas used in the dry etching described above, as long as fluorine (F) iscontained. Such a fluorine-based gas includes, for example, CHF₃, CF₄,C₂F₆, C₄F₈, and SF₆. Particularly, the fluorine-based gas free of C canfurther reduce the damage on a glass substrate since it has a relativelylow etching rate in the glass substrate.

The phase shift mask 200 of the present invention is manufactured usingthe mask blank 100 mentioned above. Therefore, in the phase shift filmhaving the transfer pattern formed therein (phase shift pattern), atransmittance with respect to the ArF exposure light is not less than10% and not more than 20%, and a phase difference between the exposurelight transmitted through the phase shift pattern and the exposure lighttransmitted through the air for the same distance as the thickness ofthe phase shift pattern is within the range of not less than 150 degreesand not more than 190 degrees, so that the high phase shift effect canbe generated. Additionally, upon the EB defect repair applied to a blackdefect found in the mask inspection during manufacture of the phaseshift mask 200, the etching end point can be relatively easily detected.

[Manufacture of Semiconductor Device]

The method for manufacturing a semiconductor device of the presentinvention is featured in that the above described phase shift mask 200,or the phase shift mask 200 manufactured using the above described maskblank 100 is used to transfer the transfer pattern to the resist film onthe semiconductor substrate by exposure. Since the phase shift mask 200of the present invention generates the high phase shift effect, when thephase shift mask 200 of the present invention is used for the exposuretransfer to the resist film on the semiconductor device, the pattern canbe formed in the resist film on the semiconductor device with theaccuracy that sufficiently satisfies the design specification. Further,even if the phase shift mask in which the black defect portion has beencorrected by the EB defect repair during its manufacture is used for theexposure transfer to the resist film on the semiconductor device, it ispossible to prevent the transfer failure from being caused in the resistfilm on the semiconductor device corresponding to the pattern portion ofthe phase shift mask where the black defect has been present. Therefore,if a circuit pattern is formed by dry-etching a processed film usingthis resist pattern as a mask, a highly accurate circuit pattern withhigh yield can be formed without disconnection and short-circuit ofwires caused by poor accuracy or transfer failure.

EXAMPLES

The embodiment of the present invention is described more specificallybelow based on examples.

Example 1

[Manufacture of Mask Blank]

The transparent substrate 1 was prepared, which had a main surfacedimension of about 152 mm×about 152 mm and a thickness of about 6.35 mm,and was made of synthetic quartz glass. The transparent substrate 1 hadbeen polished to have surface roughness not exceeding a predeterminedvalue (root mean square roughness Rq of 0.2 nm or less) in its end facesand main surfaces, and then subjected to predetermined cleaning anddrying processes.

Next, the transparent substrate 1 was placed in a single-wafer DCsputtering apparatus, a mixed target of molybdenum (Mo) and silicon (Si)(Mo:Si=8 atom %:92 atom %) was used, and the reactive sputtering (DCsputtering) using a mixed gas of argon (Ar), nitrogen (N₂), oxygen (O₂),and helium (He) as a sputtering gas was conducted, such that the phaseshift film 2 made of molybdenum, silicon, nitrogen, and oxygen (MoSiONfilm) and having a thickness of 74 nm was formed on the transparentsubstrate 1. Through the above procedure, the single-layer phase shiftfilm 2 having the thickness of 74 nm was formed in contact with asurface of the transparent substrate 1.

Then, the transparent substrate 1 with the phase shift film 2 formedthereon was subjected to a heat treatment in order to reduce film stressof the phase shift film 2 and form an oxidized layer on a surface layer.In particular, a heating furnace (electric furnace) was used to conductthe heat treatment at a heating temperature of 450° C. in the air forone hour. Another transparent substrate 1, which had had the phase shiftfilm 2 formed on its main surface under the same conditions and beensubjected to the heat treatment, was prepared. The transmittance andphase difference of the phase shift film 2 with respect to the light ata wavelength of 193 nm were measured using a phase shift amountmeasurement apparatus (MPM193 manufactured by Lasertec Corporation). Asa result, the transmittance was 12.3%, and the phase difference was176.5 degrees (deg). Further, after analyzing the phase shift film 2 bya scanning transmission electron microscope (STEM) and EDX, formation ofthe oxidized layer having a thickness of about 1.5 nm measured from thesurface of the phase shift film 2 was confirmed. Additionally, aspectroscopic ellipsometer (M-2000D manufactured by J. A. Woollam) wasused to measure the optical properties of this phase shift film 2. As aresult, at a wavelength of 193 nm, the refractive index n was 2.33, andthe extinction coefficient k was 0.42 (the refractive index n andextinction coefficient k for each thin film described below was measuredusing the same spectroscopic ellipsometer).

Still another transparent substrate 1, which had had the phase shiftfilm 2 formed thereon by the procedure similar to the above, wasprepared, the film composition in the phase shift film 2 was measured byX-ray photoelectron spectroscopy (XPS), and the measured results wererevised (calibrated) to correspond to the Rutherford backscatteringspectrometry (RBS) measured results. As a result, the composition in thephase shift film 2 other than the oxidized layer in its surface layerwas 2.8 atom % for Mo, 43.4 atom % for Si, 14.0 atom % for O, and 39.8atom % for N. Therefore, Mo/(Mo+Si) is 6.1%, and Si/O is 3.1 in thephase shift film 2. Further, any composition gradient in the filmthickness direction was not particularly found in the phase shift film 2other than the oxidized layer in its surface layer.

Then, the transparent substrate 1 with the phase shift film 2 formedthereon was placed in the single-wafer DC sputtering apparatus, achromium (Cr) target was used, and the reactive sputtering (DCsputtering) using a mixed gas of argon (Ar), carbon dioxide (CO₂),nitrogen (N₂), and helium (He) as a sputtering gas was conducted, suchthat the lowermost layer of the light shielding film 3 made of CrOCN andhaving a thickness of 16 nm was formed on the phase shift film 2. Thelowermost layer had the refractive index n of 2.29 and extinctioncoefficient k of 1.00 with respect to the light at a wavelength of 193nm. Next, the same chromium (Cr) target was used, and the reactivesputtering (DC sputtering) using the mixed gas of argon (Ar), carbondioxide (CO₂), nitrogen (N₂), and helium (He) as a sputtering gas wasconducted, such that a lower layer of the light shielding film 3 made ofCrOCN and having a thickness of 41 nm was formed on the lowermost layerof the light shielding film 3. The lower layer had the refractive indexn of 1.80 and extinction coefficient k of 1.22 with respect to the lightat a wavelength of 193 nm.

Next, the same chromium (Cr) target was used, and the reactivesputtering (DC sputtering) using a mixed gas of argon (Ar) and nitrogen(N₂) as a sputtering gas was conducted, such that an upper layer of thelight shielding film 3 made of CrN and having a thickness of 6 nm wasformed on the lower layer of the light shielding film 3. The upper layerhad the refractive index n of 1.51 and extinction coefficient k of 1.60with respect to the light at a wavelength of 193 nm. By the abovemethod, the light shielding film 3 made of the chromium-based materialand having the total thickness of 63 nm was formed, which had thethree-layer structure comprised of, from the phase shift film 2 side,the lowermost layer made of CrOCN, the lower layer made of CrOCN, andthe upper layer made of CrN. The optical density (OD) of the laminatedstructure of the phase shift film 2 and the light shielding film 3 at awavelength of 193 nm as measured was 3.0 or more.

Further, the transparent substrate 1 with the phase shift film 2 and thelight shielding film 3 laminated thereon was placed in a single-wafer RFsputtering apparatus, a silicon dioxide (SiO₂) target was used, and theRF sputtering using the argon (Ar) gas as a sputtering gas wasconducted, such that the hard mask film 4 made of silicon and oxygen andhaving a thickness of 5 nm was formed on the light shielding film 3. Bythe above method, the mask blank 100 was manufactured, which includedthe single-layer phase shift film 2, the light shielding film 3 of athree-layer structure, and the hard mask film 4 laminated on thetransparent substrate 1.

[Manufacture of Phase Shift Mask]

Then, the mask blank 100 of Example 1 was used to manufacture the phaseshift mask 200 of Example 1 through the following procedure. First, theHMDS treatment was applied to a surface of the hard mask film 4.Subsequently, the resist film made of a chemically amplified resist forelectron beam drawing and having a thickness of 80 nm was formed incontact with the surface of the hard mask film 4 by the spin coatingmethod. Then, a first pattern, which was a phase shift pattern to beformed in the phase shift film 2, was drawn on the resist film withelectron beams, and the predetermined development process was conducted,thereby forming a first resist pattern 5 a having the first pattern (seeFIG. 2(a)). In the first pattern drawn with electron beams at thispoint, a programmed defect was added in addition to the phase shiftpattern to be originally formed, so that a black defect was formed inthe phase shift film 2.

Next, the dry etching with a CF₄ gas using the first resist pattern 5 aas a mask was conducted, so that the first pattern (hard mask pattern 4a) was formed in the hard mask film 4 (see FIG. 2(b)).

Next, the first resist pattern 5 a was removed by ashing or by a peelingliquid and the like. Subsequently, the dry etching with a mixed gas ofchlorine and oxygen (gas flow ratio of Cl₂:O₂=4:1) using the hard maskpattern 4 a as a mask was conducted, so that the first pattern (lightshielding pattern 3 a) was formed in the light shielding film 3 (seeFIG. 2(c)).

Then, the dry etching with the fluorine-based gas (SF₆+He) using thelight shielding pattern 3 a as a mask was conducted, so that the firstpattern (phase shift pattern 2 a) was formed in the phase shift film 2,and at the same time the hard mask pattern 4 a was removed (see FIG.2(d)).

Next, the resist film made of the chemically amplified resist forelectron beam drawing and having a thickness of 150 nm was formed on thelight shielding pattern 3 a by the spin coating method. Then, a secondpattern, which was a pattern (light shielding pattern) to be formed inthe light shielding film 3, was drawn on the resist film by exposure,and a predetermined treatment such as development was conducted, so thata second resist pattern 6 b having the light shielding pattern wasformed (see FIG. 2(e)). Subsequently, the dry etching with the mixed gasof chlorine and oxygen (gas flow ratio of Cl₂:O₂=4:1) using the secondresist pattern 6 b as a mask was conducted, so that the second pattern(light shielding pattern 3 b) was formed in the light shielding film 3(see FIG. 2(f)). Further, the second resist pattern 6 b was removed, anda predetermined treatment such as cleaning was carried out, so that thephase shift mask 200 was obtained (see FIG. 2(g)).

The half tone phase shift mask 200 of Example 1 manufactured wassubjected to mask pattern inspection by a mask inspection apparatus, anda black defect was confirmed in the phase shift pattern 2 a at alocation where the programmed defect had been arranged. After the blackdefect portion was subjected to the EB defect repair using the electronbeams and XeF₂ gas, the etching end point managed to be detected easily,and the etching on the surface of the transparent substrate 1 managed tobe minimized.

Using AIMS193 (manufactured by Carl Zeiss), a simulation of a transferimage upon the exposure transfer to the resist film on the semiconductordevice with the exposure light at a wavelength of 193 nm was performedon the half tone phase shift mask 200 of Example 1 after the EB defectrepair. As a result of inspection of the image by the exposure transferin this simulation, it was found that the design specification wassatisfied sufficiently. Further, the transfer image of the portionsubjected to the EB defect repair was comparable to the transfer imagesof the other regions. It can be considered from this result that thecircuit pattern finally formed on the semiconductor device may havegreat accuracy, even if the phase shift mask of Example 1 after the EBdefect repair is set on a mask stage of an exposure apparatus to performthe exposure transfer to the resist film on the semiconductor device.

Example 2

[Manufacture of Mask Blank]

The transparent substrate 1 was prepared by a procedure similar toExample 1. Next, the transparent substrate 1 was placed in thesingle-wafer DC sputtering apparatus, a mixed target of molybdenum (Mo)and silicon (Si) (Mo:Si=8 atom %:92 atom %) was used, and the reactivesputtering (DC sputtering) using the mixed gas of argon (Ar), nitrogen(N₂), oxygen (O₂), and helium (He) as a sputtering gas was conducted,such that the phase shift film 2 made of molybdenum, silicon, nitrogen,and oxygen (MoSiON film) and having a thickness of 74 nm was formed onthe transparent substrate 1. Through the above procedure, thesingle-layer phase shift film 2 having the thickness of 74 nm was formedin contact with a surface of the transparent substrate 1.

Then, the transparent substrate 1 with the phase shift film 2 formedthereon was subjected to a heat treatment in order to reduce film stressof the phase shift film 2 and form an oxidized layer on a surface layer.In particular, a heating furnace (electric furnace) was used to conductthe heat treatment at a heating temperature of 450° C. in the air for anhour and a half. Another transparent substrate 1, which had had thephase shift film 2 formed on its main surface under the same conditionsand been subjected to the heat treatment, was prepared. Thetransmittance and phase difference of the phase shift film 2 withrespect to the light at a wavelength of 193 nm were measured using thephase shift amount measurement apparatus (MPM193 manufactured byLasertec Corporation). As a result, the transmittance was 12.3%, and thephase difference was 176.4 degrees (deg). Further, after analyzing thephase shift film 2 by the scanning transmission electron microscope(STEM) and EDX, formation of the oxidized layer having a thickness ofabout 1.6 nm measured from the surface of the phase shift film 2 wasconfirmed. Additionally, the spectroscopic ellipsometer (M-2000Dmanufactured by J. A. Woollam) was used to measure the opticalproperties of this phase shift film 2. As a result, at a wavelength of193 nm, the refractive index n was 2.33, and the extinction coefficientk was 0.42.

As with Example 1, still another transparent substrate 1, which had hadthe phase shift film 2 formed thereon, was prepared, the filmcomposition in the phase shift film 2 was measured by X-rayphotoelectron spectroscopy (XPS), and the measured results were revised(calibrated) to correspond to the Rutherford backscattering spectrometry(RBS) measured results. As a result, the composition in the entire phaseshift film 2 including the oxidized layer in its surface layer was 2.7atom % for Mo, 43.4 atom % for Si, 14.4 atom % for O, and 39.5 atom %for N (however, the measured value for the surface of the phase shiftfilm 2 measured without digging the phase shift film 2 by the sputteringwas excluded from the measured results due to the profound effect ofcontamination). Therefore, Mo/(Mo+Si) is 5.9%, and Si/O is 3.0 in thephase shift film 2. Further, any composition gradient in the filmthickness direction was not particularly found in the phase shift film 2other than the oxidized layer in its surface layer.

Then, the light shielding film 3 and the hard mask film 4 were formed onthe phase shift film 2 in this order by a procedure similar toExample 1. By the above method, the mask blank 100 of Example 2 wasmanufactured, which included the single-layer phase shift film 2, thelight shielding film 3 of a three-layer structure, and the hard maskfilm 4 laminated on the transparent substrate 1.

[Manufacture of Phase Shift Mask]

Then, the mask blank 100 of Example 2 was used to manufacture the phaseshift mask 200 of Example 2 by the procedure similar to Example 1.

The half tone phase shift mask 200 of Example 2 manufactured wassubjected to the mask pattern inspection by the mask inspectionapparatus, and a black defect was confirmed in the phase shift pattern 2a at a location where the programmed defect had been arranged. After theblack defect portion was subjected to the EB defect repair using theelectron beams and XeF₂ gas, the etching end point managed to bedetected easily, and the etching on the surface of the transparentsubstrate 1 managed to be minimized.

Using AIMS193 (manufactured by Carl Zeiss), a simulation of a transferimage upon the exposure transfer to the resist film on the semiconductordevice with the exposure light at a wavelength of 193 nm was performedon the half tone phase shift mask 200 of Example 2 after the EB defectrepair. As a result of inspection of the image by the exposure transferin this simulation, it was found that the design specification wassatisfied sufficiently. Further, the transfer image of the portionsubjected to the EB defect repair was comparable to the transfer imagesof the other regions. It can be considered from this result that thecircuit pattern finally formed on the semiconductor device may havegreat accuracy, even if the phase shift mask of Example 2 after the EBdefect repair is set on the mask stage of the exposure apparatus toperform the exposure transfer to the resist film on the semiconductordevice.

Comparative Example 1

[Manufacture of Mask Blank]

The mask blank of Comparative Example 1 was an example in which the filmcomposition in the phase shift film 2 was changed from Example 1, and itwas manufactured by the method similar to Example 1 except for the phaseshift film 2. Elements constituting the phase shift film 2 ofComparative Example 1 are the same as Example 1, i.e., the phase shiftfilm 2 is made of molybdenum, silicon, nitrogen, and oxygen, and is thesingle-layer structure film (MoSiON film) similar to Example 1. However,its component ratio (film composition) was changed by modifying the filmforming conditions. In particular, the transparent substrate 1 wasplaced in the single-wafer DC sputtering apparatus, a mixed sinteredtarget of molybdenum (Mo) and silicon (Si) (Mo:Si=4 atom %:96 atom %)was used, and the reactive sputtering (DC sputtering) using the mixedgas of argon (Ar), nitrogen (N₂), oxygen (O₂), and helium (He) as asputtering gas was conducted, such that the phase shift film 2 made ofmolybdenum, silicon, nitrogen, and oxygen and having a thickness of 66nm was formed. The material composition in the phase shift film 2 wasadjusted by changing the gas flow rate, etc. to be different fromExample 1.

The phase shift film 2 was also subjected to the heat treatment underthe treatment conditions similar to Example 1. Another transparentsubstrate 1, which had had the phase shift film 2 of Comparative Example1 formed on its main surface under the same conditions and beensubjected to the heat treatment, was prepared. The transmittance andphase difference of the phase shift film 2 with respect to the light ata wavelength of 193 nm were measured using the phase shift amountmeasurement apparatus (MPM193 manufactured by Lasertec Corporation). Asa result, the transmittance was 12.1%, and the phase difference was177.1 degrees (deg). Further, after analyzing the phase shift film 2 bySTEM and EDX, formation of the oxidized layer having a thickness ofabout 1.7 nm measured from the surface of the phase shift film 2 wasconfirmed. Additionally, the spectroscopic ellipsometer was used tomeasure the optical properties of the phase shift film 2. As a result,the refractive index n was 2.48 and the extinction coefficient k was0.45 with respect to the light at a wavelength of 193 nm.

Still another transparent substrate 1, which had had the phase shiftfilm 2 formed thereon by the procedure similar to the above, wasprepared, the film composition in the phase shift film 2 was measured byXPS, and the measured results were revised (calibrated) to correspond tothe RBS measured results. As a result, the composition in the phaseshift film 2 other than the oxidized layer in its surface layer was 1.9atom % for Mo, 47.1 atom % for Si, 16.1 atom % for O, and 34.9 atom %for N. Therefore, Mo/(Mo+Si) is 3.9%, and Si/O is 2.9 in the phase shiftfilm 2. Further, any composition gradient in the film thicknessdirection was not particularly found in the phase shift film 2 otherthan the surface layer portion.

Through the above procedure, the mask blank of Comparative Example 1 wasmanufactured, which included the phase shift film 2 made of MoSiON, thelight shielding film 3, and the hard mask film 4 laminated on thetransparent substrate 1 (synthetic quartz glass).

[Manufacture of Phase Shift Mask]

Next, the mask blank 100 of Comparative Example 1 was used tomanufacture a phase shift mask 200 of Comparative Example 1 by themethod similar to Example 1.

The half tone phase shift mask 200 of Comparative Example 1 manufacturedwas subjected to the mask pattern inspection by the mask inspectionapparatus, and a black defect was confirmed in the phase shift pattern 2a at a location where the programmed defect had been arranged. While theblack defect portion was subjected to the EB defect repair, it wasdifficult to detect the etching end point, and the etching proceededfrom the surface of the transparent substrate 1.

Using AIMS193 (manufactured by Carl Zeiss), a simulation of a transferimage upon the exposure transfer to the resist film on the semiconductordevice with the exposure light at a wavelength of 193 nm was performedon the half tone phase shift mask 200 of Comparative Example 1 after theEB defect repair. As a result of inspection of the image by the exposuretransfer in this simulation, it was found that the design specificationwas generally satisfied sufficiently, except for the portion subjectedto the EB defect repair. However, the transfer image of the portionsubjected to the EB defect repair was at the level that a transferfailure would be caused due to an influence of etching on thetransparent substrate 1, etc. It can be expected from this result thatwhen the phase shift mask 200 of Comparative Example 1 after the EBdefect repair was set on the mask stage of the exposure apparatus toperform the exposure transfer to the resist film on the semiconductordevice, disconnection and short-circuit are found in a circuit patternfinally formed on the semiconductor device.

Comparative Example 2

[Manufacture of Mask Blank]

The mask blank of Comparative Example 2 was an example in which the filmcomposition in the phase shift film 2 was changed from Example 1, and itwas manufactured by the method similar to Example 1 except for the phaseshift film 2. Elements constituting the phase shift film 2 ofComparative Example 2 are the same as Example 1, i.e., the phase shiftfilm 2 is made of molybdenum, silicon, nitrogen, and oxygen, and is thesingle-layer structure film (MoSiON film) similar to Example 1. However,its component ratio (film composition) was changed by modifying the filmforming conditions. In particular, the transparent substrate 1 wasplaced in the single-wafer DC sputtering apparatus, a mixed sinteredtarget of molybdenum (Mo) and silicon (Si) (Mo:Si=4 atom %:96 atom %)was used, and the reactive sputtering (DC sputtering) using the mixedgas of argon (Ar), nitrogen (N₂), oxygen (O₂), and helium (He) as asputtering gas was conducted, such that the phase shift film 2 made ofmolybdenum, silicon, nitrogen, and oxygen and having a thickness of 66nm was formed. The material composition in the phase shift film 2 wasadjusted by changing the gas flow rate, etc. to be different fromExample 1.

This phase shift film 2 was also subjected to the heat treatment underthe treatment conditions similar to Example 2. Another transparentsubstrate 1, which had had the phase shift film 2 of Comparative Example2 formed on its main surface under the same conditions and beensubjected to the heat treatment, was prepared. The transmittance andphase difference of the phase shift film 2 with respect to the light ata wavelength of 193 nm were measured using the phase shift amountmeasurement apparatus (MPM193 manufactured by Lasertec Corporation). Asa result, the transmittance was 12.1%, and the phase difference was177.0 degrees (deg). Further, after analyzing the phase shift film 2 bySTEM and EDX, formation of the oxidized layer having a thickness ofabout 1.8 nm measured from the surface of the phase shift film 2 wasconfirmed. Additionally, the spectroscopic ellipsometer was used tomeasure the optical properties of the phase shift film 2. As a result,the refractive index n was 2.48 and the extinction coefficient k was0.45 with respect to the light at a wavelength of 193 nm.

Still another transparent substrate 1, which had had the phase shiftfilm 2 formed thereon by the procedure similar to the above, wasprepared, the film composition in the phase shift film 2 was measured byXPS, and the measured results were revised (calibrated) to correspond tothe RBS measured results. As a result, the composition in the entirephase shift film 2 including the oxidized layer in its surface layer was1.9 atom % for Mo, 46.8 atom % for Si, 16.6 atom % for O, and 34.7 atom% for N (however, the measured value for the surface of the phase shiftfilm 2 measured without digging the phase shift film 2 by the sputteringwas excluded from the measured results due to the profound effect ofcontamination). Therefore, Mo/(Mo+Si) is 3.9%, and Si/O is 2.8 in thephase shift film 2. Further, any composition gradient in the filmthickness direction was not particularly found in the phase shift film 2other than the surface layer portion.

Through the above procedure, the mask blank of Comparative Example 2 wasmanufactured, which included the phase shift film 2 made of MoSiON, thelight shielding film 3, and the hard mask film 4 laminated on thetransparent substrate 1 (synthetic quartz glass).

[Manufacture of Phase Shift Mask]

Next, the mask blank 100 of Comparative Example 2 was used tomanufacture a phase shift mask 200 of Comparative Example 2 by themethod similar to Example 1.

The half tone phase shift mask 200 of Comparative Example 2 manufacturedwas subjected to the mask pattern inspection by the mask inspectionapparatus, and a black defect was confirmed in the phase shift pattern 2a at a location where the programmed defect had been arranged. While theblack defect portion was subjected to the EB defect repair, it wasdifficult to detect the etching end point, and the etching proceededfrom the surface of the transparent substrate 1.

Using AIMS193 (manufactured by Carl Zeiss), a simulation of a transferimage upon the exposure transfer to the resist film on the semiconductordevice with the exposure light at a wavelength of 193 nm was performedon the half tone phase shift mask 200 of Comparative Example 2 after theEB defect repair. As a result of inspection of the image by the exposuretransfer in this simulation, it was found that the design specificationwas generally satisfied sufficiently, except for the portion subjectedto the EB defect repair. However, the transfer image of the portionsubjected to the EB defect repair was at the level that a transferfailure would be caused due to an influence of the etching on thetransparent substrate 1, etc. It can be expected from this result thatwhen the phase shift mask 200 of Comparative Example 2 after the EBdefect repair was set on the mask stage of the exposure apparatus toperform the exposure transfer to the resist film on the semiconductordevice, disconnection and short-circuit are found in a circuit patternfinally formed on the semiconductor device.

DESCRIPTION OF REFERENCE NUMERALS

-   1: transparent substrate-   2: phase shift film-   2 a: phase shift pattern-   3: light shielding film-   3 a, 3 b: light shielding pattern-   4: hard mask film-   4 a: hard mask pattern-   5 a: first resist pattern-   6 b: second resist pattern-   100: mask blank-   200: phase shift mask

What is claimed is:
 1. A mask blank comprising a phase shift film on atransparent substrate, wherein a transmittance of the phase shift filmwith respect to exposure light of an ArF excimer laser is at least 10%and not more than 20%, and wherein the phase shift film is configured togenerate a phase difference of not less than 150 degrees and not morethan 190 degrees between the exposure light transmitted through thephase shift film and the exposure light transmitted through the air forthe same distance as a thickness of the phase shift film; wherein thephase shift film is made of a material containing a metal, silicon,nitrogen, and oxygen; wherein a ratio of the content of the metal in thephase shift film to the total content of the metal and silicon in thephase shift film is not less than 5% and not more than 10%; wherein theoxygen content in the phase shift film is 10 atom % or more; and whereinthe silicon content in the phase shift film is three times or more theoxygen content in the phase shift film.
 2. The mask blank according toclaim 1, wherein the oxygen content in the phase shift film is 20 atom %or less.
 3. The mask blank according to claim 1, wherein the nitrogencontent in the phase shift film is 30 atom % or more.
 4. The mask blankaccording to claim 1, wherein the nitrogen content in the phase shiftfilm is 45 atom % or less.
 5. The mask blank according to claim 1,wherein the phase shift film is formed in contact with a surface of thetransparent substrate.
 6. The mask blank according to claim 1, whereinthe phase shift film has a thickness of 90 nm or less.
 7. The mask blankaccording to claim 1, wherein a surface layer of the phase shift filmincludes a layer having an oxygen content higher than the oxygen contentin a portion of the phase shift film that excludes the surface layer. 8.The mask blank according to claim 1, comprising a light shielding filmon the phase shift film.
 9. A phase shift mask comprising a phase shiftfilm with a transfer pattern formed therein on a transparent substrate,wherein a transmittance of the phase shift film with respect to exposurelight of an ArF excimer laser is at least 10% and not more than 20%, andwherein the phase shift film is configured to generate a phasedifference of not less than 150 degrees and not more than 190 degreesbetween the exposure light transmitted through the phase shift film andthe exposure light transmitted through the air for the same distance asa thickness of the phase shift film; wherein the phase shift film ismade of a material containing a metal, silicon, nitrogen, and oxygen;wherein a ratio of the content of the metal in the phase shift film tothe total content of the metal and silicon in the phase shift film isnot less than 5% and not more than 10%; wherein the oxygen content inthe phase shift film is 10 atom % or more; and wherein the siliconcontent in the phase shift film is three times or more the oxygencontent in the phase shift film.
 10. The phase shift mask according toclaim 9, wherein the oxygen content in the phase shift film is 20 atom %or less.
 11. The phase shift mask according to claim 9, wherein thenitrogen content in the phase shift film is 30 atom % or more.
 12. Thephase shift mask according to claim 9, wherein the nitrogen content inthe phase shift film is 45 atom % or less.
 13. The phase shift maskaccording to claim 9, wherein the phase shift film is formed in contactwith a surface of the transparent substrate.
 14. The phase shift maskaccording to claim 9, wherein the phase shift film has a thickness of 90nm or less.
 15. The phase shift mask according to claim 9, wherein asurface layer of the phase shift film includes a layer having an oxygencontent higher than the oxygen content in a portion of the phase shiftfilm that excludes the surface layer.
 16. The phase shift mask accordingto claim 9, comprising, on the phase shift film, a light shielding filmwith a light shielding band pattern formed therein.
 17. A method formanufacturing a semiconductor device, comprising using the phase shiftmask according to claim 9 to transfer the transfer pattern to a resistfilm on a semiconductor substrate by exposure.